1. Field of the Invention
This invention relates generally to the reproduction of video signals, and more particularly, is directed to the reduction of cross-talk in the reproduction of signals recorded in adjacent tracks.
2. The Prior Art
It is well-known to record video signals on magnetic tape or other forms of record medium by scanning successive parallel tracks on the record medium with one or more transducers energized by the video signals. There has been a constant effort to improve the efficiency of use of the record medium by packing the tracks as close together as possible. The packing density has always been limited by, among other things, the fact that, during reproduction of the recorded signals, a reproducing transducer scanning each of the tracks in order could pick up signals or cross-talk from adjacent tracks.
One effort made to minimize cross-talk has been to use two transducers having air gaps with different azimuth angles for successive lines. This is relatively easy to do because most magnetic recording apparatus for video signals includes a rotary drum provided with two transducers or heads which can have gaps with different azimuth angles. The tape is wrapped helically about a portion of the perimeter of the drum and moved longitudinally along this helical path while the transducers or heads are rotated, thus bringing the heads alternately into recording relationship with the tape and allowing each head to trace out a respective one of the tracks. Each transducer or head has a finite width and thus produces magnetization of those magnetic domains in the material on the tape in what would appear to be, if such domains were visible, a series of parallel lines or stripes, each having a length as great as the width of the track, and each having an orientation that corresponds to the azimuth angle of the gap of the transducer or head used to record that track.
By recording successive alternate tracks with transducers or heads having different azimuth angles, and in view of the fact that the reproducing transducers or heads would also have corresponding azimuth angles, the gap of the reproducing transducers or heads would be aligned with the parallel, but fictitious, lines of the track being scanned thereby, but, because of the difference in azimuth angles, would extend at an angle to such lines of the next adjacent track. If the reproducing transducer overlapped that adjacent track, the well-known azimuth loss would result in attenuation of the signal reproduced from the adjacent track. Even if the reproducing transducer accurately scans a track recorded with the same azimuth, the reproducing transducer may still be influenced by the signals recorded in adjacent tracks with different azimuths, but the azimuth loss will decrease or eliminate the effect of such signals recorded in adjacent tracks on the output signal of the transducer.
Even in the above type of recording with different azimuth angles, there is still a limit to the overlapping of adjacent tracks. In the case where the video signals are not recorded with H-alignment, which means that horizontal synchronizing signals of the video signals recorded in the adjacent tracks are aligned in traverse direction of the tracks, the relatively large frequency differences occur between the signal being reproduced from a track being scanned and the cross-talk from the adjacent tracks. By reason of such relatively large frequency differences, the resulting relatively high level interfering signals cannot be sufficiently eleminated by the azimuth loss.